During the course of Sunday's Yankees-Rays game in the wilds of Florida (NYY-TB GameTracker), Rays fly-catcher Kevin Kiermaier bounced a pitch from CC Sabathia off the plate. And that's where our (very brief) story begins ... 

Executive summary: Kiermaier fouled a ball off the plate, and after re-entering Kiermaier's personal atmosphere konked him on the top floor. It did not hurt all that much, presumably -- he had the helmet on, in accordance with best practices -- but he was observably startled, as though he'd just learned that the call was coming from inside the house. 

Life comes at you fast, you see. So do baseballs. Even when baseballs are coming at you slowly, they come at you fast. Something like that. Wear a helmet even when you sleep, is the lesson here.